Pleione 6(1): 5 - 26. 2012. ISSN: 0973-9467 © East Himalayan Society for Spermatophyte A checklist of orchids in Tinsukia District of Assam, India

Khyanjeet Gogoi Daisa Bordoloi Nagar, Talap, Tinsukia- 786156, Assam, India E-mail: [email protected] Revised 04.05.2012; Accepted 05.06.2012

Abstract Tinsukia District has a vast stretch of forest cover with varied vegetation; those host many interesting species of orchids. This paper deals with the orchid flora of this district that consists of 95 species covering 48 genera, including terrestrial and epiphytic and concerned with morphological and ecological notes. Key words: Orchid Flora, Tinsukia, Distribution, Enumeration

INTRODUCTION The is one of the most highly specialized and larger families of flowering represented by more than 17000 species in nearly 1000 genera in the world and more and more new ones are being added every day (Chowdhery 1998). According to Kumar & Manilal (1994) 1141 species of Orchids in 166 genera are recorded from India, of which a major number of species are endemic. Out of 1141 species of Orchids reported so far from India about 800 species are from North-East India alone (Barua 2001). Assam the second largest state of India, is hosting many interesting Orchids like the other North-Eastern states. But, till date, no comprehensive record of Orchid flora of Assam is available. However according to Rao (1995) the actual enumeration of Orchids of Assam may be around 182 species covering 74 genera.

Study area Tinsukia is an extremely important district of Assam in the north-eastern part of India with an area of about 3790 sq km. The district is located at 95022/ E to 95038/ E longitude and 27023/ N to 27028/ N latitude, at a height of 147.83 to 148.30 m AMSL (Map 1). The district is bounded at north by the mighty river Brahmaputra and the state of Arunachal Pradesh, on the west by Dibrugarh district and the on the east and south by Arunachal Pradesh. The area is very rich in terms of biodiversity and is very significant so far wildlife and forests are concerned. There are 35 reserve forests with a total area of 917.31 sq km, one National Park (Dibru- Saikhowa, 340 sq km) and one Wildlife Sanctuary (Borajan Padumoni 7.2 sq km), which covers about 33 % of the geographic area of the district (Mahanta 2002). The Tinsukia district is located in the sub-tropical region which therefore experiences high rainfall and high humidity. The annual rainfall ranges from 2300 mm to 3800 mm most of it is received during June – September with little rains in winters too. The average temperature is 360 C maximum and about 80 C minimum. The ambient high temperature is often checked by frequent showers and thunderstorms. Based on the floristic composition it can be broadly classified into two forest types. The first type is Hollong Nahar forests and this type corresponds to the Assam valley tropical wet 6 Orchids of Tinsukia District of Assam evergreen forest of Champion & Seth’s (1968) revised classification of forest types. The second type is termed as Miscellaneous forests, which is further subdivided in to Mixed deciduous forests and Mixed deciduous forest with evergreen patches. The climatic ambience of different types of vegetation in Tinsukia district suits well for the occurrence of numerous species of orchids. Recorded species of orchids are distributed in almost all zones of the forest according to their temperature and light requirement which varies from species to species, and some terrestrial orchids are found only in grasslands and riverbanks. The present study attempts to provide the information on the orchid flora of Tinsukia district based on recent collections.

MATERIALS AND METHODS The present study is the result of several field trips covering all the seasons during 1996 to 2011 in different locations of Tinsukia district. The collected specimens were dissected and examined in laboratory during flowering period. Herbarium specimens were prepared by standard methods (Jain & Rao 1977). Specimens were identified with the help of literature and matched at the herbarium of department of Botany Guwahati University (GUBH) and at ASSAM. Herbarium specimens have been deposited at the GUBH. In the enumeration a generic name is accompa- nied by citation of the number of species in India and in this area and a species with author citation is supported with its flowering and habitat.

RESULTS All the species of orchids recorded from the Tinsukia district of Assam during the present taxonomic survey is enumerated below with names of genera alphabetically and, again, species under each genus alphabetically. In the enumeration while a generic name is provided with the author citation only, a species binomial is followed by author citation, protologue reference, flowering period and habitat.

ACAMPE Lindley About ten species from tropical Himalayan regions to Indochina, and SE , tropical and subtropical Africa, Madagascar, and the islands of the W Indian Ocean (Chen et al 2009); 6 species in India, 3 species in Assam, 2 in Tinsukia district. Acampe praemorsa (Roxburgh) Blatter & McCann, J. Bomb. Nat. Hist. Soc. 35: 495. 1932. Epidendrum praemorsum Roxburgh, Pl. Coromandel. 1: 34. 1795. Acampe papillosa (Lindley) Lindley, Fol. Orchid 2, 1853. Saccolabium papillosum Lindley, Edwards’s Bot. Reg. 18: t. 1552. 1833. Epiphyte; flowers 1 cm across, yellow, slightly fragrant; and yellow with reddish brown transverse stripes; lip white, slightly spotted with purple-red. Flowering: November – December. Exsiccatae: Gogoi 0031 Habitat: Epiphyte on tree trunk.

Acampe rigida (Buchanon-Humilton ex J.E. Smith) P.F. Hunt in Kew Bull. 24: 98. 1970; Chowdhery, Orch. Fl. Arunachal Prad. 41, 1998. Aerides rigida Buchanon-Humilton ex J.E. Smith in A. Rees, Cycl. 39: 12. 1818. Epiphyte; flowers yellow with purplish brown transverse stripes; lip white, with purplish brown longitudinal stripes above. Flowering: June – July. Exsiccatae: Gogoi 0020 Habitat: Epiphyte on tree trunks or large branches. Khyanjeet Gogoi 7

Map 1. Location map of Tinsukia district of Assam

ACANTHEPHIPPIUM Blume Fifteen species from S and NE India and , throughout SE Asia, to S Japan, , and the SW Pacific islands (Chen et al 2009); 3 species in India, 2 in Assam and 1 species in Tinsukia district. Acanthephippium striatum Lindley, in Edwards’s Bot. Reg. 24(Misc.): 41. 1838; Hooker f., Fl. Brit. India 5: 816. 1890. [Fig. 1] Terrestrial; flowers creamy white with parallel red venation, tubular, 3.5 – 4.5 cm across. Flowering: June – July. Exsiccatae: Gogoi 0233 Habitat: Growing in shaded and humid places in dense forests, banks of streams.

AERIDES Loureiro About 20 species in Sri Lanka, India, Nepal, Bhutan, , , , Indochina, and Malaysia to the Philippines and Indonesia (Chen et al 2009); 10 species in India, 5 species in NE India and 3 species in Tinsukia district. Aerides multiflora Roxburgh, Pl. Corom. 3: 68, t. 271. 1820. [Fig. 2] Epiphyte; flowers reddish or pinkish purple with darker spots, 2 – 2.5 cm across. Flowering: May – July. Exsiccatae: Gogoi 0034 Habitat: Shaded and humid places in dense forests, banks of streams. 8 Orchids of Tinsukia District of Assam

PLATE - I: Photographs of some orchids of Tinsukia District. Fig. 1. Acanthephippium striatum; Fig. 2. Aerides multiflora; Fig. 3. Bulbophyllum andersonii; Fig. 4. Cleisocentron pallens; Fig. 5. Coelogyne fimbriata; Fig. 6. densiflorum; Fig. 7. Dendrobium nobile; Fig. 8. Dendrobium sulcatum; Fig. 9. Pinalia acervata; Fig. 10. Eulophia dabia; Fig. 11. Habenaria stenopetala; Fig. 12. Nervilia juliana; Fig. 13. Phalaenopsis mannii; Fig. 14. Phalaenopsis parishii; Fig. 15. Rhynchostylis retusa; Fig. 16. Vanda tessellata. Aerides odorata Loureiro, Fl. Cochinch. 2: 525. 1790; Hooker f. Fl. Brit. India 6: 47. 1890. Epiphyte; flowers white with purple blotches at the extremeties, 2.2-2.5 cm across, fragrant. Flowering: May – June. Exsiccatae: Gogoi 0040 Habitat: Epiphyte in lowland forest. Aerides rosea Loddiges ex Lindley & Paxton, Fl. Gard. 2: 109. 1852; Chowdhery, Orch. Fl. Arunachal Prad. 49. 1998. Epiphyte; flowers fragrant, purplish-pink suffused with white, dark pink spotted, opening widely, about 2 cm across. Khyanjeet Gogoi 9 Flowering: May. Exsiccatae: Gogoi 0013 Habitat: Epiphyte in mixed deciduous forest and humid evergreen forest.

AGROSTOPHYLLUM Blume About 60 species in Old World tropics from the Seychelles and tropical Asia east to the Pacific islands, with the center of distribution in New Guinea (Chen et al 2009); 4 species in India, 1 in Assam and in Tinsukia district. Agrostophyllum planicaule (Wallich ex Lindley) Reichenbach f. in W.G.Walpers, Ann. Bot. Syst. 6: 909. 1864. Eria planicaulis Wallich ex Lindley, Edwards’s Bot. Reg. 26(Misc.): 8. 1840. Agrostophyllum khasianum Griffith in Calcutta J. Nat. Hist. 4: 378, t. 19. 1844. Epiphyte; flowers white, 6 – 8 mm across. Flowering: August – October. Exsiccatae: Gogoi 0132 Habitat: Epiphyte in mixed deciduous forest and humid evergreen forest.

BRYOBIUM Lindley About 20 species from Sri Lanka and SE Asia to New Guinea, NE , and the SW Pacific islands (Chen et al 2009), 1 species in Tinsukia district. Bryobium pudicum (Ridley) Y.P. Ng & P. J. Cribb, Orchid Rev. 113: 272. 2005. Eria pudica Ridley in J. Linn. Soc. 32: 294. 1896. Epiphytic; flowers pinkish white, pubescent, buff with darker Strips. Flowering: April – August. Exsiccatae: Gogoi 0495 Habitat: Epiphyte in deciduous forest and evergreen forest.

BULBOPHYLLUM du Petit-Thouars About 1,900 species largely in tropical areas of both Old and New Worlds (Chen et al 2009); 100 species in India and Assam represent 24 species, 7 species in Tinsukia district. Bulbophyllum affine Lindley, Gen. Sp. Orchid. 48. 1830; Hooker f., Fl. Brit. India 5: 756. 1890. Epiphyte; flowers white with pink lined, about 3 cm long, solitary. Flowering: June – August. Exsiccatae: Gogoi 0098 Habitat: Epiphyte in mixed deciduous forest and humid evergreen forest.

Bulbophyllum andersonii (Hooker f.) J.J. Smith in Bull. Jard. Bot. Buitenz. Ser. 2, 8: 22. 1912; Seidenfaden, Nots. Cirrhopetalum Lindl. 67. 1987. Cirrhopetalum andersonii Hooker f., Fl. Brit. India 5: 777. 1890. [Fig. 3] Epiphyte; flowers 1.5 cm long; Sepals and petals whitish, densely spotted with purplish red; lip purple. Flowering: October. Exsiccatae: Gogoi 0112 Habitat: Epiphyte in mixed deciduous forest and humid evergreen forest.

Bulbophyllum careyanum (Hooker) Sprengel, Syst. Veg. ed. 16 (3): 732. 1826; Hooker f., Fl. Brit. India 5: 760. 1890. Anisopetalon careyanum Hooker, Exot. Fl. 2: t. 149. 1825. Epiphyte; flowers purplish-brown, 0.5 – 0.8 cm long. Flowering: October – December. Exsiccatae: Gogoi 0176 10 Orchids of Tinsukia District of Assam Habitat: Epiphyte on tree trunks in dense humid evergreen forest.

Bulbophyllum delitescens Hance in J. Bot. 14: 44. 1876; Seidenfaden, Not. Cirrhopetalum Lindl. 215. 1987. Epiphyte; flowers reddish-brown. Flowering: June – July. Exsiccatae: Gogoi 0021 Habitat: Epiphyte in dense humid evergreen forest near a waterfall

Bulbophyllum odoratissimum (J.E. Smith) Lindley, Gen. Sp. Orchid. Pl.:55. 1830; Lindl. Gen. Sp. Orchid. 55. 1830; Hooker f., Fl. Brit. India 5: 758. 1890. Stelis odoratissima J.J. Smith in A. Rees, Cycl. 34: 12. 1816. Epiphyte; flower 5-7 mm long, white, fragrant. Flowering: May – September. Exsiccatae: Gogoi 0029 Habitat: Epiphyte in dense humid evergreen forest near a waterfall. Bulbophyllum roxburghii (Lindley) Reichenbach f. in W.G.Walpers, Ann. Bot. Syst. 6: 263. 1861; Cirrhopetalum roxburghii Lindley, Gen. Sp. Orchid. Pl.: 58. 1830; Bulbophyllum sikkimense (King & Pantling) J.J.Smith, Bull. Jard. Bot. Buitenzorg, II, 8: 28. 1912. Epiphyte; Inflorescence umbellate; flowers small, dirty brown or pale rosy, spotted with purple. Flowering: April – July. Exsiccatae: Gogoi 0721 Habitat: Epiphytic in evergreen forest. Bulbophyllum spathulatum (Rolfe ex E. Cooper.) Seidenfaden in Bot. Tidsskr. 65: 347. 1970; Chowdhery, Orch. Fl. Arunachal Prad. 146. 1998. Cirrhopetalum spathulatum Rolfe ex E. Cooper, Orchid Rev. 37: 106. 1929. Epiphyte; flowers rose red, deeply spotted, 1.6 cm long. Flowering: April. Exsiccatae: Gogoi 0276 Habitat: Epiphytic in evergreen forest.

CALANTHE R. Brown About 150 species in tropical and subtropical Asia, Australia, New Guinea, and the SW Pacific islands, as well as tropical Africa and Central and NW South America (Chen et al 2009); 23 species in India, 9 in Assam and 1 in Tinsukia district. Calanthe sylvatica (Thouars) Lindley, Gen. Sp. Orchid. Pl.: 250. 1833. Centrosis sylvatica Thouars, Hist. Orchid.: t. 35, 36. 1822. Calanthe masuca (D. Don) Lindley, Gen. Sp. Orchid. 249. 1830; Hooker f., Fl. Brit. India 5: 850. 1890. Bletia masuca D. Don, Prodr. Fl. Nepal. 30. 1825. Terrestrial; flowers pale pinkish purple with purple lip sometimes flushed with orange. Flowering: August – September. Exsiccatae: Gogoi 0161 Habitat: Terrestrial in damp places.

CALLOSTYLIS Blume About six species in China, Himalayan region, India, Indonesia, , Malaysia, Myanmar, Thailand, (Chen et al 2009); 1 species in India, Assam and Tinsukia district.

Callostylis rigida Blume, Bijdr. 7: 340. 1825. Tylostylis discolor (Lindley) Hooker f. in Ann. Roy. Bot. Gard. Calcutta 5: 22. 1895. Eria discolor Lindley, J. Proc. Linn. Soc., Bot. 3: 51. 1858. Khyanjeet Gogoi 11 Epiphytic; flowers greenish yellow, 1.2–1.5 cm across. Flowering: January – March. Exsiccatae: Gogoi 0201 Habitat: Epiphytic on trees in mixed forests.

CERATOSTYLIS Blume About 100 species in tropical Asia to New Guinea and the Pacific islands (Chen et al 2009); 1 species in India, Assam and also in the Tinsukia district. Ceratostylis subulata Blume, Bijdr. 7: 206. 1825; Chowdhery, Orch. Fl. Arunachal Prad. 167. 1998. Epiphyte; flowers greenish yellow or yellow. Flowering: May – August. Exsiccatae: Gogoi 0154 Habitat: Epiphyte in dense humid evergreen forest.

CLEISOCENTRON Bruhl 1 species only in Indo- East Asia (Misra 2007), 1 in Assam and Tinsukia district.

Cleisocentron pallens (Cathcart ex Lindley) N. Pearce & P.J. Cribb, Edinburgh J. Bot. 58: 118. 2001. Saccolabium pallens Cathcart ex Lindley, J. Proc. Linn. Soc., Bot. 3(9): 35. 1858. Cleisocentron trichromum (Reichenbach f.) Bruhl, Guid. Orch. Sikkim 137. 1926. Saccolabium trichromum Reichenbach f., Hamburger Garten- Blumenzeitung 15: 51. 1859. [Fig. 4] Epiphyte; flowers pinkish, 2.5-2.8 cm across; sepals and petals pale-straw coloured, with a middle pink band. Flowering: June – July. Exsiccatae: Gogoi 0230 Habitat: Epiphytic on tree trunks evergreen forests.

CLEISOSTOMA Blume About 100 species in Sri Lanka, India, mainland SE Asia, Malaysia, and Indonesia to the Philippines, New Guinea, Pacific islands, and Australia (Chen et al 2009); 19 species in India among them 5 species in Tinsukia district. Cleisostoma appendiculatum (Lindley) Bentham & Hooker f. ex Jackson in Index Kew. 1: 555. 1893; Chowdhery, Orch. Fl. Arunachal Prad. 200. 1998. Aerides appendiculata Lindley, Gen. Sp. Orchid. Pl.: 242. 1833. Epiphyte; flowers 1.5 cm across, sepals and petals buff with purple longitudinal lines. Flowering: August – October. Exsiccatae: Gogoi 0030 Habitat: Epiphytic on tree trunks in evergreen forests. Cleisostoma filiforme (Lindley) Garay in Bot. Mus. Leafl. Harvard Univ. 23(4): 171. 1972; Chowdhery, Orch. Fl. Arunachal Prad. 204. 1998. Sarcanthus filiformis Lindley, Edwards’s Bot. Reg. 28(Misc.): 61. 1842. Epiphyte; flowers about 1.3 cm across; sepals and petals yellowish green, with purplish brown stripes; lip white with purple-red midlobe, column yellow. Flowering: April – June. Exsiccatae: Gogoi 0494 Habitat: Epiphytic on tree trunks in evergreen forests. Cleisostoma paniculatum (Ker-Gawler) Garay in Bot. Mus. Leafl. Harvard Univ. 23(4): 173. 1972; Chowdhery, Orch. Fl. Arunachal Prad. 204. 1998. Aerides paniculata Ker Gawler, Bot. Reg. 3: t. 220. 1817. 12 Orchids of Tinsukia District of Assam Epiphytic; flowers opening widely; sepals and petals yellowish green with purple blotches within; lip yellow. Flowering: September – February. Exsiccatae: Gogoi 0707 Habitat: Epiphytic on tree trunks in evergreen forests. Cleisostoma simondii (Gagnepain) Seidenfaden, in Dansk Bot. Arkiv 29(3): 66. 1975; Chowdhery, Orch. Fl. Arunachal Prad. 208. 1998. Vanda simondii Gagnepain, Bull. Mus. Natl. Hist. Nat. ser., 2, 22: 628. 1950. Epiphytic; flowers yellowish green with purple markings. Flowering: August – October. Exsiccatae: Gogoi 0044 Habitat: Epiphyte on thick-barked tree trunks in evergreen and deciduous forest. Cleisostoma subulatum Blume, Bijdr. 363. 1825; Chowdhery, Orch. Fl. Arunachal Prad. 208. 1998. Epiphyte; flowers about 1 cm across, sepals and petals yellow with intra marginal brown bands, lip white at the base. Flowering: May – June. Exsiccatae: Gogoi 0014 Habitat: Epiphyte on tree trunk in dense humid evergreen forest.

COELOGYNE Lindley About 200 species in tropical and subtropical Asia to Oceania (Chen et al 2009); 43 species in India, 15 in Assam and 2 in Tinsukia district. Coelogyne fimbriata Lindley, Edwards’s Bot. Reg. 11: t. 868. 1825; Hooker f., Fl. Brit. India 5: 836. 1890. [Fig. 5] Epiphytic; flowers 3 – 4 cm across, pale-yellow; sepals and petals yellowish; lip yellowish, fimbriate at margins, keels 3 brownish; lip and column base brownish. Flowering: October – December. Exsiccatae: Gogoi 0709 Habitat: Epiphyte on tree trunk in dense humid evergreen forest. Coelogyne ovalis Lindley, Bot. Reg. 24: 91. Misc. 191. 1838; Hooker f., Fl. Brit. India 5: 836. 1890. Epiphyte; flowers greenish yellow, with purplish stripes on lip. Flowering: August – December. Exsiccatae: Gogoi 0485 Habitat: Epiphyte on tree trunk in dense humid evergreen forest.

COLLABIUM Blume Eleven species in SE Asia, from the to SE China, Malaysia, Indonesia, and the Philippines, to New Guinea and the Pacific islands (Chen et al 2009); 6 species in India, 3 in Assam, 1 species in Tinsukia district. Collabium chinense (Rolfe) Tang & F.T. Wang, in Fl. Hainan. 4: 217. 1977. Nephelaphyllum chinense Rolfe, Bull. Misc. Inform. Kew 1898: 194. 1896. Chrysoglossum robinsonii Ridley in J. Fed. Mal. St. Mus. 6(3): 157. 1915. Terrestrial; flowers 2 cm across; sepals and petals green; lip white; column yellow. Flowering: June – July. Exsiccatae: Gogoi 0237 Habitat: Shaded and humid places in dense forests. Khyanjeet Gogoi 13 CREPIDIUM Blume About 280 species throughout in the Asian tropics and subtropics, Australasia, and Indian Ocean islands, with a few species in temperate Asia (Chen et al 2009); 10 species in India, 1 in Assam and in the Tinsukia district. Crepidium acuminatum (D. Don) Szlachetko, Fragm. Florist. Geobot., Suppl. 3: 123. 1995. Malaxis acuminata D. Don, Prodr. Fl. Nepal 29. 1825. Terrestrial; Flowers purplish red, 1.5 cm across. Flowering: June – July. Exsiccatae: Gogoi 0036 Habitat: Terrestrial in dense humid evergreen forest on rocky terrain, also in the lowlands.

CYMBIDIUM Swartz About 55 species in tropical and subtropical Asia, south to Papua New Guinea and Australia (Chen et al 2009); 30 species in India, 12 in Assam and 3 species in Tinsukia district. Cymbidium aloifolium (Linnaeus) Swartz in Nova Acta Regiae Soc. Sci. Upsal. 2, 6: 73. 1799; Hooker f., Fl. Brit. India 6: 10. 1890. Epidendrum aloifolium Linnaeus, Sp. Pl. ed.1: 953. 1753. Epiphytic; flowers 4-5 cm across, slightly fragrant; sepals and petals pale yellow to cream-yellow, with a broad central maroon-brown stripe; lip cream-colored. Flowering: April – May. Exsiccatae: Gogoi 0012 Habitat: Epiphyte on tree trunk in dense humid evergreen forest. Cymbidium bicolor Lindley, Gen. Sp. Orchid. 164. 1833; Hooker f., Fl. Brit. India 6: 10. 1890. Epiphytic; flowers 3–4 cm across; sepals and petals yellow with a central purplish red longitudinal stripe; lip cream-yellow. Flowering: May – June. Exsiccatae: Gogoi 0015 Habitat: Epiphyte on tree trunk in dense humid evergreen forest. Cymbidium dayanum Reichenbach f. in Gard. Chron. 710. 1869; Chowdhery, Orch. Fl. Arunachal Prad., 256, 1998. Epiphytic; flowers 4–5 cm across; sepals and petals white, with a central maroon stripe; lip maroon, tinged white at its base, Flowering: June – July. Exsiccatae: Gogoi 0035 Habitat: Epiphyte on tree trunk in dense humid evergreen forest. DENDROBIUM Swartz About 1,100 species in India across to Japan, south to Malaysia and Indonesia, east to Australia, New Guinea, and the Pacific islands (Chen et al 2009); 102 species in India and nearly 20 species grow in Assam, 13 species grow in Tinsukia district.

Dendrobium acinaciforme Roxburgh, Fl. Ind. 3: 487. 1832; Chowdhery, Orch. Fl. Arunachal Prad. 283. 1998. Epiphyte; flowers yellowish-white, about 1 cm long. Flowering: June – August. Exsiccatae: Gogoi 0117 Habitat: Epiphyte on tree trunk in dense humid evergreen forest. Dendrobium aduncum Wallich in Edwards’s Bot. Reg. 28(Misc.): 58. 1842; Hooker f., Fl. Brit. India 5: 730. 1890. 14 Orchids of Tinsukia District of Assam Epiphyte; flowers 1.2-2 cm across, pale purple; sepals and petals pale pink; lip white; column white. Flowering: May. Exsiccatae: Gogoi 0028 Habitat: Epiphyte on a small tree trunk in dense humid evergreen forest. Dendrobium aphyllum (Roxburgh) Fischer in Gamble, Fl. Pres. Madras 3: 1416. 1928; Hooker f., Fl. Brit. India 5: 738. 1890. Limodorum aphyllum Roxburgh, Pl. Coromandel 1: 34. t.41. 1795. Epiphyte; flowers, pale rose, 4.5 – 5 cm across; lip yellow. Flowering: April – May. Exsiccatae: Gogoi 0005 Habitat: Epiphyte in mixed deciduous forest or open forest. Dendrobium densiflorum Wallich ex Lindley, in Wallich, Pl. Asiat. Rar. 1: 34, t. 40. 1830; Hooker f., Fl. Brit. India 5: 748. 1890. [Fig. 6] Epiphytic, flowers yellow, 4-5 cm across; lip yellow with orange base, fimbriate. Flowering: April – July. Exsiccatae: Gogoi 0099 Habitat: Epiphyte tree trunk in dense evergreen forest. Dendrobium fimbriatum Hooker, Exot. Fl. t. 71. 1823; Hooker f., Fl. Brit. India 5: 745. 1890. Epiphytic; flowers 4 – 5 cm across, sepals and petals golden yellow; lip golden yellow, with or without maroon blotch. Flowering: March – May. Exsiccatae: Gogoi 0006 Habitat: Epiphyte in mixed deciduous forest, also in humid evergreen forest. Dendrobium fugax Reichenbach f., Gard. Chron. 1257. 1871. Flickingeria fugax (Reichenbach f.) Seidenfaden in Dansk Bot. Arkiv 34: 46. 1980. Epiphyte; flowers white, 3 – 3.5 cm across, fugacious. Flowering: March – October. Exsiccatae: Gogoi 0003 Habitat: Epiphyte in humid evergreen forest, mixed deciduous forest. Dendrobium lituiflorum Lindley, in Gard. Chron. 372. 1856; Hooker f., Fl. Brit. India 5: 740. 1890. Epiphytic; flowers 4 – 5 cm across, pale purple inner surface of lip with a deep purple spot surrounded by a white circle. Flowering: April – May. Exsiccatae: Gogoi 0007 Habitat: Epiphytic on tree trunks in open forests. Dendrobium moschatum (Buchanan-Hamilton) Swartz in Schrader, Neu. Jour. Bot. 1: 94. 1806; Chowdhery, Orch. Fl. Arunachal Prad. 311. 1998. Epidendrum moschatum Buchanan-Hamilton. in Symes, Embassy Kingdom Ava, ed. 2(3): 315. 1800. Epiphytic; flower orange yellow, 5 – 7 cm across, deep yellow disk with a pale purplish brown blotch on either side. Flowering: April – June. Exsiccatae: Gogoi 0008 Habitat: Epiphytic on tree trunks in open forests. Dendrobium nobile Lindley, Gen. Sp. Orchid. 79. 1830; Hooker f. Fl. Brit. India 5: 740. 1890. [Fig. 7] Epiphytic; flowers 5 – 7 cm across, white merging with purple at apex; lip purple at tip, at middle followed by deep purple central blotch. Flowering: April – May. Exsiccatae: Gogoi 0039 Habitat: Epiphyte in humid evergreen forest, also in the lowlands. Khyanjeet Gogoi 15 Dendrobium stuposum Lindley, in Edwards’s Bot. Reg. 24(Misc.): 52. 1838; Hooker f., Fl. Brit. India 6: 186. 1890. Epiphytic; flowers small, white with a dull yellow spot on the lip. Flowering: June – August. Exsiccatae: Gogoi 0504 Habitat: Epiphytic on tree trunks in open and mountain forests. Dendrobium sulcatum Lindley, in Edwards’s Bot. Reg. 24: t. 65. 1838; Hooker f., Fl. Brit. India 5: 749. 1890. [Fig. 8] Epiphytic, flowers golden yellow, 2.5 – 3.5 cm across; lip with red-purple markings at base. Flowering: April – May. Exsiccatae: Gogoi 0153 Habitat: Epiphytic on tree trunks in dense forests. Dendrobium terminale Parish & Reichenbach f. in Trans. Linn. Soc. 30: 149. 1874; Hooker f., Fl. Brit. India 5: 725. 1890. Epiphytic; flowers 1 – 1.2 cm long, white flushed with pink. Flowering: April – June. Exsiccatae: Gogoi 0203 Habitat: Epiphytic on tree trunks at forest. Dendrobium transparens Lindley, Gen. Sp. Orchid. 79. 1830; Hooker f., Fl. Brit. India 5: 738. 1890. Epiphytic; flowers 4 – 5 cm across; sepals and petals white tinged with purple at tips, lip white with large purple patch on the disc. Flowering: April – May. Exsiccatae: Gogoi 0009 Habitat: Epiphytic on tree trunks at forest.

DIDYMOPLEXIS Griffith About 18 species in India, S China, and Indochina to S Japan (Ryukyu Islands) and the Philippines, throughout the Malay Archipelago to Papua New Guinea, tropical Australia, and the SW Pacific islands, also in SW Africa and Madagascar (Chen et al 2009); 2 species in India, 1 in Assam and in Tinsukia district.

Didymoplexis pallens Griffith, in Calcutta Jour. Nat. Hist. 4: 383, t. 17. 1844; Hooker f., Fl. Brit. India 6: 122. 1890. Terrestrial; flowers white, 0.8 cm across. Flowering: May – June. Exsiccatae: Gogoi 0048 Habitat: Terrestrial, growing in bamboo forest.

DIENIA Lindley About 19 species throughout in the Asian tropics and subtropics and in Australia (Chen et al 2009); 3 species in India 1 in Assam and in Tinsukia District.

Dienia ophrydis (J. Koenig) Seidenfaden, Contr. Orchid Fl. Thailand 13: 18. 1997. Epidendrum ophrydis J. Koenig in A.J.Retzius, Observ. Bot. 6: 46. 1791. Malaxis latifolia J.E. Smith in Rees, Cyclop. 22(3): 1819. Terrestrial; flowers pale purple, 1 cm across. Flowering: May – June. Exsiccatae: Gogoi 0059 Habitat: Terrestrial in open humid evergreen forest. 16 Orchids of Tinsukia District of Assam ERIA Lindley Eria (s.l.) comprises ca. 370 species widespread in tropical Asia and the whole of the Malay Archipelago, east to New Guinea and Bougainville Island (Chen et al 2009); around 10 species in Assam and Tinsukia district has 3 species.

Eria connata Joseph, Hegde & Abbareddy in Bull. Bot. Surv. India 24: 114, f. 1 – 7. 1982; Chowdhery, Orch. Fl. Arunachal Prad. 361. 1998. Epiphytic; flowers creamy white, with yellow lip, about 0.5 cm across. Flowering: July – September. Exsiccatae: Gogoi 0480 Habitat: Epiphyte in dense humid evergreen forest. Eria ferruginea Lindley, in Edwards’s Bot. Reg. 25: t. 35. 1839; Hooker f., Fl. Brit. India 5: 804. 1890. Epiphytic; flowers pink, 2 cm across. Flowering: June – July. Exsiccatae: Gogoi 0046 Habitat: Epiphyte in dense humid evergreen forest. Eria lasiopetala (Willdenow) Ormerod, Opera Bot. 124: 22. 1995. Aerides lasiopetala Willdenow, Sp. Pl. 4(1): 130. 1805. Eria pubescens (Hooker f.) Lindley in J. Linn. Soc. 3: 54. 1858. Dendrobium pubescens Hooker, Exot. Fl. 2: t. 124. 1825. Epiphytic, flowers yellow, tomentose, about 1.5 cm across. Flowering: March – April. Exsiccatae: Gogoi 0004 Habitat: Epiphyte in humid evergreen forest, mixed deciduous forest.

EULOPHIA R. Brown ex Lindley About 200 species in tropical and subtropical regions, most diverse in Africa, but also widespread from Madagascar and the Mascarene Islands to Central and tropical Asia, the SW Pacific islands, and N and NW Australia (Chen et al 2009); 32 species in India; 9 species in Assam; 1 in Tinsukia district.

Eulophia dabia (D. Don) Hochreutiner, Bull. New York Bot. Gard. 6: 270. 1910. Bletia dabia D. Don, Prodr. Fl. Nepal.: 30. 1825. Eulophia hormusjii Duthie in Ann. Roy. Bot. Gard. Calcutta 9(2): 125, t. 125. 1906. [Fig. 10] Terrestrial; flowers brownish, 3-4 cm across. Flowering: August – December. Exsiccatae: Gogoi 0022 Habitat: Terrestrial, growing on open and loose soil.

GASTROCHILUS D. Don About 47 species are distributed in India, Nepal, SE Asia, Malaysia and the adjacent areas (Chen et al 2009); about 12 species in India, 3 in Assam and Tinsukia district. Gastrochilus calceolaris (Buchanon-Hamilton ex J.E. Smith) D. Don, Prodr. Fl. Nepal. 32. 1825; Chowdhery, Orch. Fl. Arunachal Prad. 413. 1998. Aerides calceolaris Buchanon-Hamilton ex J.E. Smith in A. Rees, Cycl. 39: 11. 1819. Epiphyte; flowers widely opening; sepals and petals yellow, with purplish brown markings; lip white with purple-red marks. Flowering: October – November. Exsiccatae: Gogoi 0042 Khyanjeet Gogoi 17 Habitat: Epiphyte in humid evergreen forest, mixed deciduous forest. Gastrochilus dasypogon (J.E. Smith) O. Kuntze, Rev. Gen. Pl. 2: 661. 1891; Chowdhery, Orch. Fl. Arunachal Prad. 413. 1998. Aerides dasypogon J.E. Smith in A.Rees, Cycl. 39: 10. 1819. Epiphyte; flowers yellow with brownish-purple spots, 1.5 – 2 cm across. Flowering: October – November. Exsiccatae: Gogoi 0023 Habitat: Epiphyte in humid evergreen forest, mixed deciduous forest. Gastrochilus inconspicuus (Hooker f.) O. Kuntze, Rev. Gen. Pl. 2: 661. 1891; Chowdhery, Orch. Fl. Arunachal Prad. 413. 1998. Saccolabium inconspicuum Hooker f., Fl. Brit. India 6(1): 56. 1890. Epiphyte; flowers white or yellowish-green, 0.5 cm across. Flowering: June – July. Exsiccatae: Gogoi 0019 Habitat: Epiphyte in humid evergreen forest, mixed deciduous forest.

GEODORUM G. Jackson About ten species found in from tropical Asia, as far north as S Japan (Ryukyu Islands), to Australia and the SW Pacific islands (Chen et al 2009); 1 species in India, Assam and also in Tinsukia district. Geodorum densiflorum (Lamarck) Schlechter in Fedde Report. Behi. 4: 259. 1919; Chowdhery, Orch. Fl. Arunachal Prad. 418. 1998. Limodorum densiflorum Lamarck, Encycl. 3: 516. 1792. Terrestrial; flowers white to pinkish, lip with a central yellow callus and crimson-purple venation and streaks. Flowering: June – July. Exsiccatae: Gogoi 0238 Habitat: Terrestrial in evergreen forest, also in grass land.

GOODYERA R. Brown About 100 species in S Africa, Asia, NE Australia, Europe, Madagascar, North America including Mexico, SW Pacific islands (Chen et al 2009); 17 species in India, 4 in Assam, 1 species in Tinsukia district. Goodyera procera (Ker Gawler) Hooker f., Exot. Fl. 1(3): t. 39. 1823; Hooker f., Fl. Brit. India 6: 111. 1890. Neottia procera Ker Gawler, Bot. Reg. 8: t. 639. 1822. Terrestrial; flowers fragrant, opening weakly, white tinged pale green. Flowering: April – June. Exsiccatae: Gogoi 0001 Habitat: Terrestrial at the bank of a small stream and in evergreen forest, also on rock in a stream.

HABENARIA Willdenow About 600 species worldwide, mainly in tropical and subtropical areas (Chen et al 2009); about 66 species in India; 7 in Assam; 1 in Tinsukia district. Habenaria stenopetala Lindley, Gen. Sp. Orchid. 319, 1835. [Fig. 11] Terrestrial; stem 30 – 90 cm long, clothed sheaths; tubers about 2.5 – 3 cm long; leaves many, oblong-lanceolate to ovate-lanceolate, acute, margins undulate, 8 – 15 x 2.5 – 4 cm; inflorescence dense; flowers greenish, 2.5 – 3 cm across. Flowering: August – October. Exsiccatae: Gogoi 0037 Habitat: Terrestrial in evergreen forest. 18 Orchids of Tinsukia District of Assam HETAERIA Blume About 30 species distributed in tropical Africa and Asia, extending to New Guinea, NE Australia, and the Pacific islands (Chen et al 2009); 6 species in India, 2 in Assam and 1 in Dibrugarh district. Hetaeria affinis (Griffith) Seidenfaden & Ormerod, Oasis, Suppl. 2: 9, 2001; Mishra, Orch. India, 304, 2007. Goodyera affinis Griffith, Not. Pl. Asiat. 3: 391. 1851. Flowers opening slightly, 5-6 mm across, green, tipped with pink; lip white. Flowering: January – February. Exsiccatae: Gogoi 0505 Habitat: Terrestrial, in shady areas of secondary evergreen forest.

LIPARIS L.C. Richard About 320 species growing in tropical Asia, New Guinea, Australia, SW Pacific islands, and the subtropical and tropical Americas, with a single species in Europe and two in North America (Chen et al 2009); 45 species in India, 9 in Assam and 2 in Tinsukia district. Liparis mannii Reichenbach f. in Flora 55: 275. 1872; Hooker f., Fl. Brit. India 5: 701. 1890. Epiphytic; flowers yellowish, 5 mm across. Flowering: November – January. Exsiccatae: Gogoi 0124 Habitat: Epiphyte in humid evergreen forest. Liparis viridiflora (Blume) Lindley, Gen. Sp. Orchid. Pl.: 31. 1830; Hooker f., Fl. Brit. India 5: 704. 1890. Malaxis viridiflora Blume, Bijdr.: 392. 1825. Epiphytic; flowers greenish white or pale greenish yellow. Flowering: April – May. Exsiccatae: Gogoi 0011 Habitat: Epiphyte in humid evergreen forest and mixed deciduous forest.

LUISIA Gaudichaud About 40 species in Bhutan, China, India, Indochina, Indonesia, Japan, Malaysia, New Guinea, Pacific islands, Philippines, Sri Lanka, and Thailand (Chen et al 2009); 16 species in India, 5 in Assam, 2 in Tinsukia district. trichorrhiza (Hooker) Blume Rumphia 4: 50. 1849; Hooker f., Fl. Brit. India 6: 23. 1890. Vanda trichorhiza Hooker, Exot. Fl. 1: t. 72. 1825. Epiphytic; flowers purplish green with faint purple lines, about 1.5 cm across. Flowering: March – May. Exsiccatae: Gogoi 0002 Habitat: Epiphyte in humid evergreen forest, growing on exposed trees. Luisia tristis (G. Forster) Hooker f., Fl. Brit. India 6: 25. 1890. Epidendrum triste G. Forster, Fl. Ins. Austr.: 60. 1786. Luisia zeylanica Lindley, Fol. Orchid. Luisia, 3. 1853; Chowdhery, Orch. Fl. Arunachal Prad. 501. 1998. Epiphytic; flowers greenish yellow, with purple base. Flowering: April – May. Exsiccatae: Gogoi 0496 Habitat: Epiphyte in humid evergreen forest, growing on exposed trees.

MICROPERA Lindley About 15 species is ranging from the Himalayas to SE Asia, New Guinea, Australia, and the (Chen et al 2009); 3 species in India, 3 in Assam and 1 in Tinsukia district. Khyanjeet Gogoi 19 Micropera rostrata (Roxburgh) Balakrishnan, in J. Bomb. Nat. Hist. Soc. 67: 66. 1970; Chowdhery, Orch. Fl. Arunachal Prad. 512. 1998. Aerides rostrata Roxburgh, Fl. Ind. (ed. 1832), 3: 474. 1832. Epiphyte; owers pale-purple, 1.5 – 2 cm across. Flowering: April – May. Exsiccatae: Gogoi 0026 Habitat: Epiphyte on tree trunk in evergreen tropical forest.

MYCARANTHES Blume About 25 species in Bhutan, Cambodia, China, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, New Guinea, Philippines, Singapore, Thailand, Vietnam (Chen et al 2009); 2 in Tinsukia district. Mycaranthes floribunda (D. Don) S.C. Chen & J.J. Wood in Fl. China 25: 348. 2009. Dendrobium floribundum D. Don, Prodr. Fl. Nepal.: 34. 1825. Eria paniculata Lindley in Wallich, Pl. Asiat. Rar. 1: 32, t. 36. 1830; Hooker f., Fl. Brit. India 5: 789. 1890. Epiphytic; flowers yellowish green. Flowering: December – March. Exsiccatae: Gogoi 0225 Habitat: Epiphyte in dense humid evergreen forest. Mycaranthes pannea (Lindley) S.C. Chen & J.J. Wood, in Fl. China 25: 348. 2009. Eria pannea Lindley in Bot. Reg. 64. (misc.) 79. 1842; Hooker f., Fl. Brit. India 5: 804. 1890. Epiphytic; flowers pale yellow-green, lip dark purplish. Flowering: May – July. Exsiccatae: Gogoi 0147 Habitat: Epiphyte in dense evergreen forest.

NERVILIA Commerson ex Gaudichaud About 65 species in tropical and subtropical Africa, Madagascar, and parts of the Arabian Peninsula, across India, Nepal, and Bhutan to Japan, SE Asia, New Guinea, N Australia, and the SW Pacific islands (Chen et al 2009); 14 species in India, 3 in Assam, 1 in Tinsukia district. Nervilia juliana (Roxburgh) Schlechter in Engler, Bot. Jahrb. Syst. 45: 402. 1911; Chowdhery, Orch. Fl. Arunachal Prad. 529. 1998. Epipactis juliana Roxburgh, Fl. Ind. (ed. 1832), 3: 453. 1832. [Fig. 12] Terrestrial; flowers purple-green, solitary; lip white, mottled with pink. Flowering: May – July. Exsiccatae: Gogoi 0047 Habitat: Terrestrial, growing on open and loose soil. OBERONIA Lindley About 150 species centered in tropical S and SE Asia but extending to tropical Africa, Madagascar, the Mascarene Islands, the Philippines, New Guinea, NE Australia, and the SW Pacific islands across to Tahiti (Chen et al 2009); 50 species in India, 13 in Assam, 1 in Tinsukia district. Oberonia mucronata (D. Don) Ormerod & Seidenfaden in Seidenfaden, Contr. Orchid Fl. Thailand 13: 20. 1997; Mishra, Orch. India 309. 2007. Stelis mucronata D. Don, Prodr. Fl. Nepal.: 32. 1825. Epiphytic; flowers yellowish. Flowering: September – October. Exsiccatae: Gogoi 0032 Habitat: Epiphyte on tree trunk in evergreen tropical forest. PAPILIONANTHE Schlechter About 12 species in China, India, SE Asia and the Malay Archipelago (Chen et al 2009); 4 species in India, 2 in Assam, 1 in Tinsukia district. 20 Orchids of Tinsukia District of Assam Papilionanthe teres (Roxburgh) Schlechter, in Orchis 9: 78, t.12. 1915; Chowdhery, Orch. Fl. Arunachal Prad. 570. 1998. Dendrobium teres Roxburgh, Fl. Ind. (ed. 1832), 3: 485. 1832. Epiphyte; flowers 5–10 cm across; sepals and petals white, tinged with pink or purplish; lip deep purple-red. Flowering: April – May. Exsiccatae: Gogoi 0010 Habitat: Epiphyte in mixed deciduous forest, also on solitary roadside trees.

PHAIUS Loureiro About 40 species in tropical Africa, Madagascar, tropical and subtropical Asia to Oceania (Chen et al 2009); 7 species in India, 4 in Assam, 2 in Tinsukia district. Phaius mishmensis Reichenbach f. in Bonplandia 5: 43. 1857; Hooker f., Fl. Brit. India 5: 817. 1890. Terrestrial; flowers 4 – 5 cm across, white, greenish yellow or pinkish purple. Flowering: November – January. Exsiccatae: Gogoi 0484 Habitat: Terrestrial, on the bank of a small stream in dense humid evergreen forest. Phaius tankervilleae (Banks ex L’ Heritier) Blume, Mus. Bot. Lugd.- Bat. 2: 177. 1856; Chowdhery, Orch. Fl. Arunachal Prad. 583. 1998. Limodorum tankervilleae Banks ex L’ Heritier, Sert. Angl.: 28. 1789. Terrestrial; flowers 7–12 cm across; sepals and petals whitish outside, reddish brown or brown inside; lip white toward base, pink or red-pink toward entrance with white stripes on inside. Flowering: November – January. Exsiccatae: Gogoi 0512 Habitat: Terrestrial, shaded and damp places in forests.

PHALAENOPSIS Blume About 45 species from India to S China, Thailand, Indochina, Malaysia, and Indonesia to the Philippines and New Guinea, the majority in Indonesia and the Philippines (Chen et al 2009); 7 species in India, 5 in Assam, 3 in Tinsukia district. Phalaenopsis deliciosa Reichenbach f., Bonplandia (Hannover) 2: 93. 1854. Kingidium deliciosum (Reichenbach f.) Sweet in Amer. Orchid Soc. Bull. 39: 1095. 1970. Epiphytic; flowers greenish yellow; lip purple spotted. Flowering: May – July. Exsiccatae: Gogoi 0016 Habitat: Epiphyte in gallery forest along a large river, in a shady spot in humid evergreen forest. Phalaenopsis mannii Reichenbach f., Gard. Chron. 1871: 902. 1871; Hooker f., Fl. Brit. India, 6: 30, 1890. [Fig. 13] Epiphytic; flowers 3 – 4 cm across; sepals and petals yellow with dark brown spots and bars; mid-lobe of lip white; column yellow. Flowering: March – May. Exsiccatae: Gogoi, 0344 Habitat: Epiphytic on tree trunks in evergreen forests. Phalaenopsis parishii Reichenbach f., Bot. Zeitung (Berlin) 23: 146. 1865; Hooker f., Fl. Brit. India 6: 31. 1890. [Fig. 14] Epiphyte; flowers white with two chestnut bands on lip, 2 cm across. Flowering: March – April. Exsiccatae: Gogoi, 0258 Habitat: Epiphytic on tree trunks in open forests. Khyanjeet Gogoi 21 PHOLIDOTA Lindley ex Hooker f. About 30 species in mainland and SE Asia, Australia, New Guinea, and the Pacific islands (Chen et al 2009); 10 species in India, 7 in Assam, 2 in Tinsukia district. Pholidota articulata Lindley, Gen. Sp. Orchid. 38,1833; Hooker f., Fl. Brit. India, 5: 844, 1890. Epiphytic; flowers greenish white or white and slightly tinged with reddish, 5 mm across. Flowering: July – October. Exsiccatae: Gogoi 0435 Habitat: Epiphyte in dense humid evergreen forest close to a waterfall. Pholidota imbricata Lindley in W.J. Hooker, Exot. Fl. 2: t. 138. 1825; Hooker f., Fl. Brit. India 5: 845. 1890. Epiphyte; flowers white, 5 mm across. Flowering: June – August. Exsiccatae: Gogoi 0018 Habitat: Epiphyte on tree humid evergreen forest.

PINALIA Lindley About 160 species from NW Himalayas and NE India to Myanmar, S China, Vietnam, Laos, Thailand, the Malay Archipelago, NE Australia, and the Pacific islands (Chen et al 2009); 3 in Tinsukia district. Pinalia acervata (Lindley) Kuntze, Revis. Gen. Pl. 2: 679. 1891. Eria acervata Lindley in J. Hort. Soc. 6: 57. 1851. [Fig. 9] Epiphytic; flowers white, about 1.5 cm across. Flowering: May – July. Exsiccatae: Gogoi 0501 Habitat: Epiphyte in dense humid evergreen forest. Pinalia amica (Reichenbach f.) Kuntze, Revis. Gen. Pl. 2: 679. 1891. Eria amica Reichenbach f., Xen. Orchid. 2: 162, t. 168. f. 6 – 9. 1870. Epihytic; flowers pale-yellow, with reddish- brown nerves, about 1.2 cm across. Flowering: March – May. Exsiccatae: Gogoi 0482 Habitat: Epiphyte in dense humid evergreen forest. Pinalia pumila (Lindley) Kuntze, Revis. Gen. Pl. 2: 679. 1891. Eria pumila Lindley, Gen. sp. Orchid 68. 1830; Hooker f., Fl. Brit. India 5: 791. 1890. Epiphytic; flowers white, flushed with pink. Flowering: January – March. Exsiccatae: Gogoi 0045 Habitat: Epiphyte in humid evergreen forest, mixed deciduous forest.

PODOCHILUS Blume About 60 species from India and Sri Lanka to China, south and east through Indonesia and New Guinea to the Pacific islands (Chen et al 2009); 4 species in India, 2 in Assam and Tinsukia district. Podochilus cultratus Lindley, Gen Sp. Orchid. 234. 1833; Hooker f., Fl. Brit. India 6: 80. 1890. Epiphytes; flowers white, 5 mm long. Flowering: April – May. Exsiccatae: Gogoi 0497 Habitat: Epiphyte on tree trunk in wet evergreen tropical forest. 22 Orchids of Tinsukia District of Assam Podochilus khasianus Hooker f., Fl. Brit. India 6: 81. 1890; Chowdhery, Orch. Fl. Arunachal Prad. 616. 1998. Epiphytes; flowers white, very small. Flowering: June – August. Exsiccatae: Gogoi 0400 Habitat: Epiphyte on tree trunk in wet evergreen tropical forest.

POMATOCALPA Breda, Kuhl & Hasselt Thirteen species from India through Malesia and N Australia to , north to NE Himalayas and Taiwan (Chen et al 2009); 8 species in India, 1 in Assam and Tinsukia district. Pomatocalpa undulatum (Lindley) J.J. Smith, Natuurw. Tijdschr. Ned.-Indie 72: 107. 1912; Chowdhery, Orch. Fl. Arunachal Prad. 622. 1998. Pomatocalpa undulatum (Lindley) T. Tang & F.T. Wang in Acta. Phytotax. Sin. 1(1 – 2): 100. 1951. Saccolabium undulatum Lindley, Gen. Sp. Orchid. Pl.: 222. 1833. Epiphyte; flowers 8 mm across, yellow with purple blotched; lip with purple blotched. Flowering: March – May. Exsiccatae: Gogoi 0033. Habitat: Epiphyte in the wet evergreen tropical forest.

RHYNCHOSTYLIS Blume About three or four species from Sri Lanka, India through mainland SE Asia, China, the Philippines, south through Malaysia and Indonesia (Chen et al 2009); 2 species in India, 1 in Assam as well as in Tinsukia district. Rhynchostylis retusa (Linnaeus) Blume, Bijdr. 286, t. 49. 1825; Hooker f., Fl. Brit. India 6: 32. 1890. Epidendrum retusum Linnaeus, Sp. Pl. 2: 953. 1753. Rhynchostylis albiflora Borua & Bora in J. Econ. Taxon. Bot. 26(1): 251 - 255. 2002. Rhynchostylis retusa f. albiflora (Barua & Bora) Christenson, J. Orchideenfr. 12: 344. 2005. [Fig. 15] Epiphyte; flowers 1.7 – 2.3 cm across; flowers white or white and spotted with pink or pale purple. Flowering: May – June. Exsiccatae: Gogoi 0017. Habitat: Epiphyte in the evergreen tropical forest, mixed deciduous forest and also on solitary roadside trees.

ROBIQUETIA Gaudichaud About 40 species from the Himalayas to Australia and the SW Pacific islands, with a few species extending to Indochina and China (Chen et al 2009); 4 species in India, 2 in Assam, 1 in Tinsukia district. Robiquetia spatulata (Blume) J.J. Smith in Nat. Tijdschr. Ned. Ind. 72: 114. 1912; Chowdhery, Orch. Fl. Arunachal Prad. 630. 1998. Cleisostoma spatulatum Blume, Bijdr.: 364. 1825. Epiphytic; flowers yellow with purplish brown spots and stripes. Flowering: May – July. Exsiccatae: Gogoi 0027. Habitat: Epiphyte humid evergreen forest.

SPIRANTHES Richard About 50 species distributed in America, Europe, Asia, Pacific Island and Australia (Chen et al 2009); 2 species in India, 1 in Assam and Tinsukia district. Spiranthes sinensis (Persoon) Ames, Orch. 2: 53. 1908. Neottia sinensis Persoon, Syn. Pl. 2: 511. 1807. Khyanjeet Gogoi 23 Terrestrial, 10-40cm high; leaves 3-5 in basal rosette, 5-15x0.5-1cm, acute, oblong-elliptic or lanceolate; inflorescence densely many flowered, with spirally arranged flowers; flowers white, with white lip. Flowering: Febuary-April. Exsiccatae: Gogoi 0043. Habitat: Terrestrial in open grassland.

TAINIA Blume About 32 species in Sri Lanka and India, north to China and Japan, south from Myanmar to New Guinea and the Pacific islands (Chen et al 2009); 9 species in India, 3 in Assam and 2 in Tinsukia district. Tainia latifolia (Lindley) Reichenbach f., Bonplandia (Hannover) 5: 54. 1857; Hooker f., Fl. Brit. India 5: 820. 1890. Ania latifolia Lindley, Gen. Sp. Orchid. Pl.: 130. 1831. Terrestrial; flowers 2 cm across, dark brown, lip yellow. Flowering: March – May. Exsiccatae: Gogoi 0350. Habitat: Terrestrial in dense humid evergreen forest. Tainia minor Hooker f. in Fl. Brit. India 5: 821. 1890; Chowdhery, Orch. Fl. Arunachal Prad. 661. 1998. Terrestrial; flowers 1.5 cm across, purplish brown with deep purple spots; lip white, tinged with purplish brown. Flowering: June – August. Exsiccatae: Gogoi 0488. Habitat: Terrestrial in dense humid evergreen forest.

THELASIS Blume About 20 species from India eastward to New Guinea and the Pacific islands (Chen et al 2009); 4 species in India, 2 in Assam and 1 in Tinsukia district. Thelasis longifolia Hooker f. in Fl. Brit. India 6: 87. 1890; Chowdhery, Orch. Fl. Arunachal Prad. 662. 1998. Epiphytic, flowers green, not opening widely, small. Flowering: June – August. Exsiccatae: Gogoi 0355. Habitat: Epiphytic in evergreen forest.

THRIXSPERMUM Loureiro About 100 species distributed in Sri Lanka and the Himalayan region east to the Pacific islands, with an apparent center of distribution in Sumatra (Chen et al 2009); 9 species in India, 6 in Assam and 1 in Tinsukia district. Thrixspermum centipeda Loureiro, Fl. Cochinch. 520. 1790; Chowdhery, Orch. Fl. Arunachal Prad. 665. 1998. Epiphytic; flowers white or creamy yellow, turning yellow later. Flowering: May – August. Exsiccatae: Gogoi 0430. Habitat: Epiphyte in mixed deciduous forest, in humid evergreen forest.

TRICHOTOSIA Blume About 50 species distributed in mainland Asia through SE Asia to New Guinea and the Pacific islands (Chen et al 2009); 3 species in India, 1 in Assam and in Tinsukia district. 24 Orchids of Tinsukia District of Assam Trichotosia velutina (Loddiges ex Lindley) Kranzlin in Engler & Prantl, Nat. Pflanzen. 50: 140. 1911; Chowdhery, Orch. Fl. Arunachal Prad. 672. 1998. Eria velutina Loddiges ex Lindley, Edwards’s Bot. Reg. 26: Misc. 86. no. 209 1840. Epiphytic; flowers pale- white, 1 cm across. Flowering: August – September. Exsiccatae: Gogoi 0391. Habitat: Epiphyte on tree trunks in humid forest.

TROPIDIA Lindley About 20 species distributed mainly in tropical and subtropical Asia, with a few species extending to Australia and the Pacific islands and one in Central and North America (Chen et al 2009); 3 species in India, 2 in Assam and 1 in Tinsukia district. Tropidia curculigoides Lindley, Gen. Sp. Orchid. 497. 1840; Chowdhery, Orch. Fl. Arunachal Prad. 676. 1998. Terrestrial; flowers greenish white, 1.5 cm long. Flowering: September – November. Exsiccatae: Gogoi 0479. Habitat: Terrestrial in dense humid evergreen forest and evergreen forest.

VANDA Jones ex R. Brown About 40 species in tropical Asia to New Guinea and Australia (Chen et al 2009); 12 species in India, 2 species in Tinsukia. Vanda tessellata (Roxburgh) Hooker f. ex G. Don in J.C. Loudon, Hort. Brit.: 372. 1830. Epidendrum tessellatum Roxburgh, Pl. Coromandel 1: 34. t.42. 1795. [Fig. 16] Epiphytic; flowers 4 – 5 cm across, yellow with brown tessellation, lip white with speckled with violet inside. Flowering: April – June. Exsiccatae: Gogoi 0113. Habitat: Epiphytic on trees in mixed forests. Vanda testacea (Lindley) Reichenbach f. in Gard. Chron. 8: 166. 1877. Aerides testacea Lindley, Gen. Sp. Orchid. Pl.: 238. 1833. Epiphytic; flowers yellow, about 1.5 cm across; sepals and petals yellow. Flowering: May – June. Exsiccatae: Gogoi 0118. Habitat: Epiphytic on tree trunks in dense forests.

ZEUXINE Lindley About 80 species in tropical and S Africa, through tropical and subtropical Asia, to New Guinea, NE Australia, and the SW Pacific islands (Chen et al 2009); 19 species has been estimated from India, 11 species in Assam, 4 in Tinsukia district. Zeuxine glandulosa King & Pantling in Ann. Roy. Bot. Gard. (Calcutta) 8: 288, t. 384 (1898). Type: India, Duars, Pantling 434. Heterozeuxine glandulosa (King & Pantling) Hashimoto, Proc. 14th World Orchid conf.: 125. 1993. Terrestrial, 5-20 cm long; flowers olivaceous green, column and central contracted part of lip white; pedicel and ovary glandular-pubescent. Flowering: March- April. Exsiccatae: Gogoi 0511. Habitat: Growing in dense forest, cool and shady place. Khyanjeet Gogoi 25 Zeuxine goodyeroides Lindley, Gen. Sp. Orchid. 486. 1840; Hooker f., Fl. Brit. India 6: 107. 1890. Terrestrial; flowers resupinate, white, small. Flowering: January – February. Exsiccatae: Gogoi 0025. Habitat: Growing in dense forest, cool and shady place. Zeuxine lindleyana A.N. Rao in Arunachal For. News 6(1): 34. 1988. Terrestrial; flowers pale white with pinkish tinge, 1 – 2.5cm long, not fully opening. Flowering: March – April. Exsiccatae: Gogoi, 0038. Habitat: Terrestrial, growing in grass land. Zeuxine strateumatica (Linnaeus) Schlechter in Engler, Bot. Jahrb. 45: 394. 1911; Chowdhery, Orch. Fl. Arunachal Prad. 695. 1998. Orchis strateumatica L., Sp. Pl.: 943. 1753. Terrestrial; flowers small, resupinate, white, lip pale yellow to yellow. Flowering: January – March. Exsiccatae: Gogoi 0024. Habitat: Terrestrial, growing in grass land.

DISCUSSION In the present study the occurrence of 95 species covering 48 genera of orchids are reported growing in the Tinsukia district of Assam. Out of these, 73 are epiphytic and 22 are terrestrial. A few species of orchids such as, Acampe papilliosa, Acanthephippium striatum, Aerides odorata, Bulbophyllum affine, B. spathulatum, Cleisocentron pallens, Cymbidium dayanum, Dendrobium densiflorum, D. nobile, Gastrochillus calceolaris, Liparis mannii, Phaius mishmensis, Phalaenopsis mannii, P. parishii, Vanda tessellata, V. testacea, Zeuxine lindleyana are very rare in Tinsukia Didtrict. Dendrobium densiflorum, Vanda tessellata and V. testacea found only in the border area of the Tinsukia and Arunachal Pradesh. Bulbophyllum roxburghii a newly recorded species (Nath & Das 2011) is very common in the border area of the Tinsukia and Arunachal Pradesh. Out of 48 genera present, Dendrobium is the largest with 13 species. A good number of species like Aerides multiflorum, A. rosea, A. odorata, Cymbidium bicolor, C. dayanum, Dendrobium moschatum, D. densiflorum, D. fimbriatum, D. nobile, D. transparens, D. lituiflorum, D. aphyllum, D. aduncum, D. sulcatum, Micropera rostratum, Phaius tankervilleae, Rhynchostylis retusa etc. produce beautiful ornamental flowers. So far only 22 species of ground orchids have been collected from the Tinsukia district. However, it is expected that some more such orchids will be recorded from the diverse vegetation types in different corners of the district. Tinsukia is not a very big district and there is no extreme variation in topography. Also, there is no recognizable hill area. Even then, the flora of the district is extremely rich and that is also reflected in its recorded orchid flora. Large scale destruction of forests and other type of vegetation during the past few decades have resulted in drastic depletion of orchids in Tinsukia. Since supporting trees are needed for epiphytic orchids, deforestation has severely affected the diversity of orchids. It is therefore desirable to conserve the valuable orchid flora of this region through ex-situ as well as in-situ conservation methods. To conserve the orchids, it is necessary to conserve their habitats, and necessity to recognize the host plants and increasing the population of such species in orchid rich areas. Acknowledgements The author is grateful to Dr. G. C. Sharma, Department of Botany, Guwahati University and the authorities of the Department of Forest, Tinsukia, Assam for constant supervision and valuable suggestions during the course of investigation. 26 Orchids of Tinsukia District of Assam LITERATURE CITED

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